On 11.01.22 00:15, Matthew Wilcox (Oracle) wrote:
> Move the compound page overrun detection out of
> CONFIG_HARDENED_USERCOPY_PAGESPAN and convert it to use folios so it's
> enabled for more people.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> mm/usercopy.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/mm/usercopy.c b/mm/usercopy.c
> index dcf71b7e3098..e1cb98087a05 100644
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -164,7 +164,6 @@ static inline void check_page_span(const void *ptr, unsigned long n,
> {
> #ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN
> const void *end = ptr + n - 1;
> - struct page *endpage;
> bool is_reserved, is_cma;
>
> /*
> @@ -195,11 +194,6 @@ static inline void check_page_span(const void *ptr, unsigned long n,
> ((unsigned long)end & (unsigned long)PAGE_MASK)))
> return;
>
> - /* Allow if fully inside the same compound (__GFP_COMP) page. */
> - endpage = virt_to_head_page(end);
> - if (likely(endpage == page))
> - return;
> -
> /*
> * Reject if range is entirely either Reserved (i.e. special or
> * device memory), or CMA. Otherwise, reject since the object spans
> @@ -259,6 +253,10 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
> if (folio_test_slab(folio)) {
> /* Check slab allocator for flags and size. */
> __check_heap_object(ptr, n, folio_slab(folio), to_user);
> + } else if (folio_test_large(folio)) {
> + unsigned long offset = ptr - folio_address(folio);
Nit: I'd have added an empty line.
> + if (offset + n > folio_size(folio))
> + usercopy_abort("page alloc", NULL, to_user, offset, n);
> } else {
> /* Verify object does not incorrectly span multiple pages. */
> check_page_span(ptr, n, folio_page(folio, 0), to_user);
LGTM
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
